ESTRO 2025 - Abstract Book

S1243

Clinical – Lower GI

ESTRO 2025

fosters new therapeutic approaches. The present work aims to report the ten-year experience of a single large volume RT Department, to take a picture of clinical practice in this scenario.

Material/Methods: Pts who completed a neoadjuvant SCRT course followed by surgery between 2012 and 2021 were retrospectively collected. RT was performed using IMRT or 3D-CRT scheduled in 25 Gy/5 fr. Post-operative complications were graded according to the Clavien-Dindo Classification. Association of pts, tumor, and treatment characteristics with overall survival (OS), postoperative complications, and downstaging were also investigated. Results: Sixty-four pts met the inclusion criteria. The choice of SCRT was mainly driven by comorbidities, advanced age, and/or the presence of metastasis at diagnosis. Forty-three (67%) pts had LARCs, while 21 (33%) were at IV stage. Twenty-two pts (34%) underwent chemotherapy before SCRT, while post-operative chemotherapy was prescribed in 20 cases (34%). Thirty-six out of 64 pts (56%) underwent immediate surgery (within 4 weeks), while 28 (44%) deferred surgery (after 4 weeks). A median follow-up of 3.0 years (IQR 1.6-4.6) was observed, and 33 pts (52%) were alive at the end of the observation period. At 1 year, local relapse incidence was 6% (95% CI: 2-14%), and OS was 92% (95% CI: 82-97%). Interestingly, OS was not found to be different stratifying pts according to the presence of metastases at diagnosis, while a trend was found between reduced OS and advanced age, male gender, increased neutrophil-lymphocyte ratio (NLR) and deferred surgery. Dividing pts according to the time of surgery (immediate vs deferred), downstaging was significantly higher in the case of deferred surgery (68% vs. 31%, p=0.003), as expected (Table 1).